An increase in the average daily weight gain of an animal is of great importance to enterprises where the body weight of the animal is necessary for the commercial success of the enterprise. Weight gain also is important for animals, including humans, who have lost weight due to a disease, a mental disorder or a medical treatment.
Attempts to enhance production performance in domestic food animals have largely focused on the use of feed efficiency enhancers including, but not limited to, formulations containing nutrients, vitamins, minerals, hormones, sulphonomides, antiprotozoals, antifungals, antivirals, antiparasitics, antibiotics and vaccines.
Hormones including, but not limited to estrogens, estradiol, progesterone, synthetic progestins, testosterone, anabolic steroids and somatotrophin production stimulants are expensive and should not be used in breeding animals. In addition, their use in food animals is unacceptable to large segments of the population and is restricted in some countries. Antiprotozoals, antifungals, antivirals, antiparasitics and antibiotics including, but not limited to, terramycin, tetracycline, virginiamycin, aureomycin and lincomycin are expensive, can be toxic to humans and cannot be used in all animal species. There is public concern regarding the overuse and misuse of antibiotics in animal husbandry, leading to development of antibiotic resistant organisms. Again, their use in food animals is unacceptable to large segments of the population and is restricted in some countries. Vaccines, used to combat specific infectious diseases in domestic food are expensive, are not available for all diseases and can result in selection of pathogenic organisms for virulency and for resistance.
Various biological and chemical immunomodulators have been used to stimulate the immune system to minimize the impact of disease in animals, including humans. These include, but are not limited to, opiod peptides, thymosins, glucocorticoids, cytokines, interferons, levamisole, isoprinosine, poynucleotides and microbial products. Microbial products that have been used as immunomodulators include, but are not limited to, heat killed or formaldehyde treated suspensions of Priopionibacterium acnes, microbial polysaccharides, lipopolysaccharides, protein-bound polysaccharides, muramyl-dipeptide, lipid A and Mycobacterium phlei cell wall extract (U.S. Pat. No. 4,744,984; U.S. Pat. No. 5,759,554).
Domestic food animals are particularly susceptible to infectious disease during the first year of life and more particularly during the neonatal period. Among calves over 70% of deaths that occur during the first year of life occur during the neonatal period when their immune system is functionally immature (Radostits et al. 1985. Herd Health W. B. Saunders, Philadelphia Pa. pgs. 116-1400). Functional immaturity of the immune system includes, but is not limited to, sub-optimal neutrophil function (Hauser et al. 1986. Am. J. Vet. Res. 47:152-153), decreased complement activity (Renshaw et al. 1978. Immunology 34:801-805), poor induction of delayed hypersensitivity reactions (Woodward et al. 1979. Am. J. Vet. Res. 40:636-644), low levels of interleukin (IL)-2 production (Griebel et al. 1987. Can. J. Vet. Res. 51:428-435) and weak lymphocyte proliferative responses (Rossi et al. 1979. Am. J. Vet. Res. 40:576-579; Rossi et al. 1981. Am. J. Vet Res. 27:1369-1370).
Because of the many diseases to which animals are vulnerable and because, during the newborn and neonatal periods, some of these diseases are exacerbated by an immature immune system, there is a need for a novel method for activating the immune system to enhance disease resistance, especially during the newborn and neonatal periods, and, thereby, to increase production performance in these animals.
This method should be relatively inexpensive to prepare, easy to administer and suitable for use in all animals. Moreover, its activity should remain stable over time, be reproducible among preparations, be effective at dose regimens associated with minimal toxicity, be safe for the consumer and be acceptable to all segments of the population.